This section is intended to provide a background or context to the invention disclosed below. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented or described. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description in this application and is not admitted to be prior art by inclusion in this section.
The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:
3GPP third generation partnership project
BS base station
DL downlink, from base station to user equipment
ECGI enhanced cell global identity
EDGE enhanced data rates for GSM evolution
eNB Node B (evolved Node B), E-UTRAN base station
EPC evolved packet core
E-UTRAN evolved UTRAN (LTE)
GERAN GSM EDGE radio access network
GSM global system for mobile communications
HO handover
LTE long term evolution of UTRAN (E-UTRAN)
LTE-A LTE advanced
MAC medium access control (layer 2, L2)
MM/MME mobility management/mobility management entity
NodeB Node B, UTRAN base station
NW network
O&M operations and maintenance
PCI physical cell identity
PDCP packet data convergence protocol
PHY physical (layer 1, L1)
RAT radio access technology
Rel release (e.g., Rel-10 is release 10)
RLF radio link failure
RNC radio network controller (UTRAN)
RSRP reference signal received power
RRC radio resource control
RRM radio resource management
TR technical report
TS technical standard
UE user equipment, such as a mobile station, mobile node or mobile terminal
UL uplink, from user equipment to base station
UTRAN universal terrestrial radio access network
X2 interface between eNBs (E-UTRAN)
One modern communication system is known as evolved UTRAN (E-UTRAN, also referred to as UTRAN-LTE or as E-UTRA). One specification of interest is 3GPP TS 36.300, V8.11.0 (2009-12), 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Access Network (EUTRAN); Overall description; Stage 2 (Release 8), incorporated by reference herein in its entirety. This system may be referred to for convenience as LTE Rel-8. In general, the set of specifications given generally as 3GPP TS 36.xyz (e.g., 36.211, 36.311, 36.312, etc.) may be seen as describing the Release 8 LTE system. More recently, Release 9 and Release 10 versions of at least some of these specifications have been published including 3GPP TS 36.300, V10.2.0 (2010-12).
FIG. 1 reproduces FIG. 4-1 of 3GPP TS 36.300 and shows the overall architecture of the EUTRAN system (Rel-8). The E-UTRAN system includes eNBs, providing the E-UTRAN user plane (PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminations towards the UEs. The eNBs are interconnected with each other by means of an X2 interface. The eNBs are also connected by means of an S1 interface to an EPC, more specifically to a MME by means of a S1 MME interface and to an S-GW by means of a S1 interface (MME/S-GW). The S1 interface supports a many-to-many relationship between MMEs/S-GWs/UPEs and eNBs.
The eNB hosts the following functions:
functions for RRM: RRC, Radio Admission Control, Connection Mobility Control, Dynamic allocation of resources to UEs in both UL and DL (scheduling);
IP header compression and encryption of the user data stream;
selection of a MME at UE attachment;
routing of User Plane data towards the EPC (MME/S-GW);
scheduling and transmission of paging messages (originated from the MME);
scheduling and transmission of broadcast information (originated from the MME or O&M); and
a measurement and measurement reporting configuration for mobility and scheduling.
Of particular interest herein are the further releases of 3GPP LTE (e.g., LTE Rel-10, LTE Rel-11) targeted towards future IMT-A systems, referred to herein for convenience simply as LTE-Advanced (LTE-A). LTE-A is specified in Rel-10 (see, e.g., 3GPP TS 36.300 v10.3.0 (2011-03)), further enhancements in Rel-11. Reference in this regard may also be made to 3GPP TR 36.913 V9.0.0 (2009-12) Technical Report 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Requirements for further advancements for Evolved Universal Terrestrial Radio Access (E-UTRA) (LTE-Advanced) (Release 9). Reference can also be made to 3GPP TR 36.912 V9.3.0 (2010-06) Technical Report 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Feasibility study for Further Advancements for E-UTRA (LTE-Advanced) (Release 9).
In this system and other systems, a UE performs a cell selection procedure according to certain standards. Cell selection may occur, for instance, in UE power on situations, in connection with handover (HO) failure situations and in connection with Radio Link Failure (RLF) where a UE is leaving one cell and is entering another cell. Cell selection is left to UE implementation.